A metal transfer trough is generally used to receive molten metal from a furnace and deliver it to a casting station, which for example carries moulds for casting metal pigs. The furnace may be used in a remelt shop or it may be fed from molten metal crucibles carrying hot metal which, in the aluminum industry, could have been siphoned directly from an aluminum electrolysis pot.
Generally, the transfer trough is insulated to ensure that the heat loss during transfer is minimized and energy is not wasted. However, in certain circumstances, the molten metal may be considered too hot for delivery to the casting station, and it is necessary to lower its temperature before delivery. Typically in such circumstances, the rate of casting is slowed down in order to allow enough time for the pigs to solidify before leaving the casting station. This brings about an undesirable reduction in the production rate of the plant. Alternatively, the holding time in the crucible is increased in order to allow the metal to cool down, which also results in production slowdowns.
Other systems for cooling molten metal during transfer are known in the art. For example, EP 0 161 051 describes a closed conduit which is immersed in a heat exchanger medium such as a fluidized bed of solid particles. Circulation of the molten metal into the conduit is effected using pressure without contact with the atmosphere. CA 2,083,919 discloses a partially inclined elongated conveying conduit for transporting molten metal within a diffusion furnace. The conduit comprises gas feed means for feeding an inert gas into the conduit, thereby forcing circulation of the molten metal.
There is a need for a system that allows for a more efficient cooling of the molten metal during transfer to the casting station and also that allows for control over the temperature of the molten metal upon delivery.